高龄白菜java学习第106天（java数据结构和算法（24））

六、普利姆算法

代码实现：

package Algorithm.Prim;

import java.util.Arrays;

public class Prim {
    public static void main(String[] args) {
        MGraph graph = new MGraph(7);
        MinTree minTree = new MinTree();
        char[] data ={'A','B','C','D','E','F','G'};
        //临界矩阵中用很大的数表示两点之间不连通
        int[][] weight = new int[][]{
                {100,5,7,100,100,100,2},
                {5,100,100,9,100,100,3},
                {7,100,100,100,8,100,100},
                {100,9,100,100,100,4,100},
                {100,100,8,100,100,5,4},
                {100,100,100,4,5,100,6},
                {2,3,100,100,4,6,100}
        };
        minTree.createTree(graph, graph.count, data,weight);
        minTree.showGraph(graph);
        minTree.prim(graph,0);
    }
}

//创建最小生成树
class MinTree{
    public void createTree(MGraph graph, int count,char[] data,int[][] weight){
//        for (int i = 0; i < data.length; i++) {
//            graph.data[i] = data[i];
//        }
        graph.data = data;
        graph.weight = weight;
        graph.count = count;
    }

    public void showGraph(MGraph graph){
        for (int[] link : graph.weight) {
            System.out.println(Arrays.toString(link));
        }
    }
    //v表示从第几个结点开始生成
    public void prim(MGraph graph,int v){
        int[] visited = new int[graph.count];
        //标记为已读
        visited[v]=1;
        //记录两个顶点的下标
        int h1 = -1;
        int h2 = -1;
        for (int k = 1; k < graph.count; k++) {//n个点对应n-1条边
            int minWeight = 100;//初始化一个较大值
            //确定每一次生成的子图，和哪个节点的距离最近
            for (int i = 0; i < graph.count; i++) {//i表示已被访问过的节点，j表示相邻未访问过的节点
                for (int j = 0; j < graph.count; j++) {
                    if (visited[i]==1&&visited[j]==0&& graph.weight[i][j]<minWeight){
                        minWeight = graph.weight[i][j];
                        h1=i;
                        h2=j;
                    }
                }
            }
            //退出循环后找到了一条边最小
            System.out.println(""+graph.data[h1]+graph.data[h2]+graph.weight[h1][h2]);
            visited[h2]=1;
        }
    }
}

class MGraph{
    int count;//表示结点的个数
    char[] data;//存放节点的数据
    int[][] weight;//邻接矩阵存储边的权值

    public MGraph(int count) {
        this.count = count;
        this.data = new char[count];
        this.weight = new int[count][count];
    }
}